Tonight, prosecutors are deciding which crime boston marathon bombing suspect dzhokar tsaranev will face. He is in serious and stable condition unable to speak. And we will not know whether there are any other imminent threats out there. All day lowe've been watch pg these riveting images. This is infrared video shot from a helicopter. It shows stun grenades lobbed into the boat where the suspect was hiding. This is a genuine moment of crisis. And abc's martha raddatz takes us inside. Reporter: The video images show the dramatic end to the manhunt more clearly than anything we have seen. The police helicopter hovers in the darkness, holding steady. The natural heat fro the suspect's body, making a near-perfect outline through thermal imaging. He is lying on his back. His head to the right, feet to the left. Then, a flash, a bang. Police toss a stun grenade, meant to confuse the suspect. Then, another. Followed by a third. And then, watch. At first, motionless. We see for the first time video as the 19-year-old raises his head, his upper body. Quite a bit of movement. Reporter: On the ground, dozens of negotiators watching from the second floor of a house nearby, urging the suspect to give up. A robot moves in to peel away the tarp. Looks like he will successfully rip that off. He will be exposed. Reporter: Dzhokar tsaranev is on the ground, receiving medical treatment. One key break in capturing the suspects cam carjacked left his cell phone in the car. And tracking that phone is what led the police to watertown and that deadly firefight with the two brothers before the younger one took off.

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